Most of gas turbine combined cycle power plants are located in urban areas to provide peak load and district heating. However, NOx(nitrogen oxides) of exhaust gas emission from the power plants cause additional fine dust and thus it has negative impact on the urban environment. Although DLN(dry low NOx) and multi-stage combustors have been widely applied to solve this problem, they have another critical problem of damages to combustors and turbine components due to combustion dynamic pressure. In this study, the effect of different fuel ratio on NOx emission and pressure fluctuation was investigated regarding two variable conditions; combustor stages and power output on M501J gas turbine.

The non-reacting flow field and the movement of sand particles inside a 30MW circulating fluidized bed combustor is numerically simulated via the finite volume method. The primary air is supplied through 23x23 array of nozzles located on the bottom and the secondary air is supplied through 12 inlet pipes located on the side walls. The steady state velocity field shows that a very complex flow pattern is formed in the lower part of the combustor. As the gas moves upward, the velocity magnitude decreases and the gas exits the combustor after hitting the top wall. To investigate the behavior of sand particles with different diameters, a particle tracking calculation is performed by introducing sand particles continuously at the z=3 m plane. For the given air flow rate condition, sand particles smaller than 0.3 mm show a complex movement pattern near the secondary air inlet and then rise toward the outlet.

The combustion instability in a dual swirl combustor was investigated experimentally. The effects of thermal power and combustor length on combustion instability were evaluated. Pressure and heat release fluctuation were measured simultaneously. In a conventional combustor, the frequency was decreased with increasing combustor length and decreasing thermal power. However, it showed different results with a dual swirl combustor. In regime 1 where thermal power was relatively high, the results showed same tendency with a conventional combustor. In regime 2 where thermal power was relatively low, the frequency was almost constant with increasing combustor length. It was found that a beating phenomenon occurred with increased combustor length in regime 2 by measuring sound pressure fluctuation. By confirming that beating phenomenon occurs only in regime 2, it is considered that beating phenomenon is the dominant factor of combustion instability in regime 2. This beating phenomenon inside combustion chamber greatly affected to combustion instability. The reason of the beating phenomenon seemed to be the difference oscillating period between main flame and pilot flame.

The energy efficiency of gas turbine using LNG as a fuel has reached to less than about 40% even for the H class gas turbine. To increase the energy efficiency, in theoretical analysis, the maximum value of fuel efficiency can be obtained via the equally large value of the mixing rate and reaction rate in the harmonic-mean type overall reaction rate expression. Even if the delayed mixing rate can be overcome successfully by the strategy of the practically proved lean-burn method, however, the critical problem caused by the retarded reaction rate caused by the excess air has to be solved in order to make any breakthrough of the engine or gas turbine fuel efficiency. To do this, a series of systematic numerical calculation has been made for the evaluation of the lean-burn CH4 flame feature with the addition of small amount of H2 or HHO (H2+1/2O2, water electrolysis gas). To maintain lean burn state, the flow rate of methane was greatly reduced less than 50% of the standard flow rate. The addition of HHO or H2 heating value has increased steadily from 5, 10 and up to 20% of the 100% CH4 flow rate. And investigation of flame characteristics such as peak flame temperature and its location together with the temperature profile has been made through numerical calculation for a gas turbine combustor. For the standard case of 100% CH4 injection, the flame temperature profile was observed to increase steadily from the primary combustor region to gas turbine inlet. This is exactly corresponds to the temperature profile appeared in a heating process with constant pressure assumption in a typical Brayton cycle. However, for the case of co-burning with H2 or HHO with only 40 and 50% CH4 injection, the peak flame temperature appears near the upstream primary region and decreases significantly along the downstream toward turbine inlet. A detailed discussion further has been made for the flame characteristics with the change of added fuel amount and its type. In summary, the addition of the H2 and HHO gas with the reduced amount of the CH4 flow rate results in quite different temperature profile expected from the standard Brayton cycle. Further this kind of flame feature suggests the possibility of high fuel efficiency together with the reduction of the metallurgical thermal damage of the turbine blade due to the decreased gas temperature near turbine inlet.

The aim of this work to investigate the distribution of mercury in the gas phase, bottom ash and fly ash during the combustion of coal and solid waste such as dried sludge and solid refuse fuel (SRF) because the solid waste can be used as alternative fuel. In our study, we used two types of continuous combustors including vertical and horizontal combustor at the same conditions. In vertical combustor, we can get only the bottom ash while in horizontal combustor we get both fly ash and bottom ash. For both combustors, the gaseous mercury was measured by using the Ontario Hydro Method. The results showed that a significant amount of emission of gas phase mercury occurs during the combustion of coal, dried sludge, and SRF. Among the fuels, SRF showed high mercury oxidation while dried sludge showed a high level of gaseous mercury emission in the flue gas.

Analyzing results of exhaust gas of solid fuel burning are investigated with measuring position in a pilot scale MILD(Moderate and Intense Low oxygen Dilution) combustor using high temperature exhaust gas recirculation. Flue gas hasbeen measured at exit of combustion chamber and stack, especially. Oxygen concentration measured at stack is higherand carbon dioxide concentration is lower than that measured at exit of combustion chamber, because air flows into theflue gas from the post-treatment facilities, such as gas cooler and bag filter, due to negative pressure caused by inducedblower. Low carbon dioxide concentration can cause an error which estimates higher air ratio than actual air flow rateneeded for complete combustion. Average calculated concentration of measured nitric oxide and carbon monoxide forreference concentration of 6% oxygen have no notable difference with measuring position. But, time resolution of thedata measured at exit of combustion chamber is better than that measured at stack. It is confirmed that MILD combustionof solid fuel of pulverized coal using high temperature exhaust gas recirculation can reduce dramatically nitric oxideemission.

In this study, a cold model of a circulating fluidized bed is developed and tested for designing a char combustor. This study has been carried out to investigate effects of the solid circulation rate and superficial gas velocity on the hydrodynamic characteristics in a circulating fluidized bed. Solid holdup and pressure drop in the riser increases with the increase of solid circulation rate, but decreases with increasing superficial gas velocity. The solid holdup in the dense region increases with increasing solid circulation rate at lower gas velocities, whereas it is independent of solids circulation rate at higher gas velocities.

The objectives of this study were to investigate the characteristics of desulfurization under different experimental conditions and the effects of desulfurization in a fluidized bed combuster installed with the screen. The experimental results were as follows ; First, as the height of fluidized bed combustor becomes higher, the concentrations of SO_2 mainly increased and sulfur retion of paper sludge was higher than that of natural limestone. Second, the desulfurization by natural limestone occurred at in-bed and the desulfurization by paper sludge occurred in the whole of fluidized bed combuster. In additiion, we identified calcium sulfate by the analysis of SEM and XRD. Third, screen at splash region increased sulfur retention 2∼5%, air velocity and anthracite fraction had a little effect on the sulfur retention.

It has been studied that combustion and the production of air pollution of anthracite - bituminous coal blend in a fluidized bed coal combustor. The objects of this study were to investigate mixing characteristics of the particles as well as the combustibility of the low grade domestic anthracite coal and imported high calorific bituminous coal in the fluidized bed coal combustor. They were used as coal samples ; the domestic low grade anthracite coal with heating value of 2,010㎉/㎏ and the imported high grade bituminous coal with heating value of 6,520㎉/㎏. Also, the effects of air flow rate and anthracite fraction on the reaching time of steady state condition have been studied. The experimental results are presented as follows. The time of reaching to steady state was affected by the temperature variation. The steady state time was about 120 minute at 300scfh which was the fastest. It has been found that O_2 and CO_2 concentration were reached steady state at about 100 minute. It has been found that O_2 concentration decreased and CO_2 concentration increased as the height of fluidized bed increased. It was found that splash zone was mainly located from 25㎝ to 35㎝ above distributor. Also, as anthracite fraction increased, the mass of elutriation particles increased, and CO_2 concentration decreased. As air flow rate increased, O_2 concentration decreased and CO_2 concentration increased. Regardless of anthracite fraction and flow rate, the uncombustible weight percentage according to average diameter of elutriation particles were approximately high in the case of fine particles. As anthracite fraction and air flow rate increased, elutriation ratio increased. As anthracite fraction was increased, exit combustible content over feeding combustible content was increased. Regardless of anthracite fraction, size distribution of bed material from discharge was almost constant. Over bed temperature 850℃ and excess air 20%, the difference of combution efficiencies were little. It is estimate that the combustion condition in anthracite-bituminous coal blend combustion is suitable at the velocity 0.3m/s, bed temperature 850℃, the excess air 20%.